UNDER THE ESTEEMED GUIDENCE OF

Mr. P.D.V.S.K.KISHORE M.Tech

By

RAKESH P

10471D4202

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VOLTAGE SAG/SWELL COMPENSATION USING Z-

SOURCE INVERTER BASED ON DYNAMIC

VOLTAGE RESTORER

ABSTRACT

• Presents the modeling and simulation of a dynamic voltage

restorer (DVR) as a voltage sag/swell mitigation device in

electrical power distribution networks.

• The dynamic voltage restorer – compensates voltage sags/swells

• A new topology based on Z-source inverter is presented.

Z-source inverter enhance the voltage restoration property of

dynamic voltage restorer and ensure a constant DC voltage across

the DC-link

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What is mean by power quality?

• The term power quality refers to maintaining asinusoidal wave form of bus voltages at ratedvoltage and frequency.

• Problems

1.voltage sag

2.voltage swell

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Voltage sagDefinition :

A voltage sag is a reduction in the RMS voltage

in the range of 0.1 to 0.9 p.u. for duration

greater than half a main cycle and less than 1

minute.

Causes: 1. sudden increasing in loads

2. Short circuits

3. faults

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Sag wave form

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Voltage swell

Definition:

A voltage swell is an increase in the RMS voltagein the range of 1.1 to 1.8 p.u. for a durationgreater than half a main cycle and less than 1minute.

Causes: 1. sudden reduction in loads.

2. energizing a large capacitor bank.

3.switching off large inductive loads.

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Voltage swell wave form

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solutions

• Power electronic devices

• Filters

• Capacitor banks

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DVR

• What is Dynamic Voltage Restorer?

o A type of FACTS device.

• What is FACTS (Flexible AC Transmission

systems)?

o Types of FACTS devices.

• Why DVR?

o compensate voltage sag/swells

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Dynamic voltage restorer

• protection of sensitive loads from sag/swell

• The Dynamic Voltage Restorer (DVR) is fast, flexible and efficient solution to voltage sag problem

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DVR circuit diagram

11Schematic diagram of DVR

Z-SOURCE INVERTER

• why we are using z-source inverter?

in VSI (O/P is lower than I/p),

And in CSI (O/P is higher than I/p).

• Z-source inverter has X-shaped impedance network on its DC

side, which interfaces the source and inverter H-bridge.

• It facilitates both voltage-buck and boost capabilities.

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General Block Diagram of Z-Source

Inverter

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What is mean by PWM?

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• Z-Source inverter operation is controlled by multiple pulse width

modulation.

multiple pulse width modulation

MULTIPLE PULSE WIDTH MODULATION

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VOLTAGE SAG COMPENSATION IN DVR SYSTEM

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Subsystem 1 OF VOLTAGE SAG COMPENSATION IN DVR SYSTEM

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Subsystem 2 OF VOLTAGE SAG COMPENSATION IN DVR SYSTEM

Simulation results for Sag

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THD For Voltage Sag

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VOLTAGE SWELL COMPENSATION IN DVR SYSTEM

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Subsystem 1 OF VOLTAGE SWELL COMPENSATION IN DVR SYSTEM

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Subsystem 2 OF VOLTAGE SWELL COMPENSATION IN DVR SYSTEM

Simulation results for SWELL

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THD For Voltage Swell

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VOLTAGE SAG COMPENSATION IN DVR USING FUZZY CONTROLLER

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INSTEAD OF PI USING FUZZY CONTROLLER

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SAG WAVE FORMS

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USING FUZZY CONTROLLER SAG THD IS

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VOLTAGE SWELL COMPENSATION IN DVR USING FUZZY CONTROLLER

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INSTEAD OF PI USING FUZZY CONTROLLER

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SWELL WAVE FORMS

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SAG OUT PUT WAVE FORMCOMPARISON

USING PI CONTROLLER USING FUZZY CONTROLLER

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THD VALUE COMPARISON B/W PI CONTROLLER AND FUZZY CONTROLLER

USING PI CONTROLLER USING FUZZY CONTROLLER

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SWELL OUT PUT WAVE FORMCOMPARISON

PI CONTROLLER FUZZY CONTROLLER

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THD VALUE COMPARISON B/W PI CONTROLLER AND FUZZY CONTROLLER

PI CONTROLLER FUZZY CONTROLLER

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CONCLUSION

• Presenting DVR is simple and efficient.

• DVR Compensates Voltage Sag.

• DVR Compensates Voltage Swell.

• Compare to PI Controller Fuzzy Controller is Best one for getting good results.

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REFERENCES

[1] Choi S. S, Li B. H, and Vilathgamuwa D. M (2000) “Dynamic voltagerestoration with minimum energy injection,” IEEE Trans. Power

Systems, vol. 15, pp. 51-57.[2] Gajanayake C. J, Vilathgamuwa D. M, and Loh P. C (2005) “Smallsignal

and signal-flow-graph modeling of switched Z-source impedancenetwork,” IEEE Power Electronics Letters, vol. 3, pp. 111-116.

[3] Jimichi T, Fujita H., and Akagi H. (2005) “Design and experimentationof a dynamic voltage restorer capable of significantly reducing anenergystorage element,” in Conf. Record Industry ApplicationsConference,14th IAS Annual Meeting..

[4] Loh P. C, Vilathgamuwa D. M, Lai Y. S, Chua G. T, and Li Y (2004)“Pulse-width modulation of Z-source inverters,” in Conf. Record IEEEIndustry Applications Conference, 39th IAS Annual Meeting.

[5] Peng F. Z. (2003) “Z-source inverter,” IEEE Trans. IndustryApplications, vol.39, pp. 504-510.

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